Field of the Invention
The present invention relates to a cutting method and cutting stage of toughened glass, and more particularly, to a cutting method and cutting stage of toughened glass with which a piece of toughened glass is divided into unit pieces of toughened glass.
Description of Related Art
Glass products are indispensable components in a variety of technological and industrial fields, involving image and optical equipment, such as monitors, cameras, video tape recorders (VTRs), mobile phones and the like, transportation equipment, such as vehicles, various types of tableware, construction facilities, and the like. Accordingly, glass products having a variety of physical properties that meet the requirements of respective industrial fields are manufactured and used.
In particular, due to rapid distribution of smart phones, the use of touch screen panels mainly in mobile displays is rapidly increasing. Since these touch screen panels require high light transmittance and mechanical endurance considering their functions, a cover glass or cover window is made of toughened glass.
Toughened glass is manufactured by a physical toughening method, also referred to as air-cooled toughening, which is mainly applied to the safety glass of a vehicle or a chemical toughening method. The chemical toughening method can be usefully applied to a thin glass sheet that has a complicated shape or a thickness of about 2 mm or less. The chemical toughening method is a technology that improves the strength and hardness of a glass by exchanging alkali ions having a small ion radius (generally Na ions) that are present inside the glass with alkali ions having a large ion radius (generally K ions) under predetermined conditions.
FIG. 1 is a conceptual view schematically showing the cross-section of a chemically-toughened glass.
As shown in FIG. 1, a compressive stress layer is formed on the surface of the chemically-toughened glass, and a tensile stress layer or a central tension layer is formed inside the glass due to the reaction. Bending strength and mechanical strength are increased by the high compressive stress of the surface.
It is difficult to mechanically cut the toughened glass or machine its contour after toughening due to its characteristics and the absence of techniques for machining them. Therefore, the toughened glass is manufactured by a method of cutting and machining a raw glass plate before toughening the glass plate. However, this method has the drawback of low productivity since production costs such as personnel expenses are high and the breakage ratio of half-finished products is high due to a large number of manual processes. Furthermore, the importance of the yield is increasing due to the increasing size of mobile displays. It is becoming more difficult to apply this method of toughening a piece of glass after cutting and machining it to a mass production process.
Accordingly, the development of technologies for cutting and machining a raw glass plate after toughening it is actively underway.
However, as for a chemically-toughened glass that has a depth of layer (DOL) of about 20 μm or greater and a surface compressive stress of 600 MPa or greater, it is generally impossible to cut the glass using a mechanical wheel.
FIG. 2 shows pictures taken from the cross-section of a piece of gorilla glass available from Corning Inc. that is cut by wheel scribing. The part (a) in FIG. 2 is a picture taken from the cross-section, and the part (b) in FIG. 2 is a picture taken from the planar surface. As shown in the part (a) in FIG. 2, it can be appreciated that a median crack is not uniformly formed when the toughened glass having a high compressive stress of 600 MPa or greater in the surface is wheel-scribed. In addition, as shown in the part (b) in FIG. 2, it can be appreciated that a large amount of chipping occurs on the surface of the toughened glass having a DOL of 20 μm or greater when it is wheel-scribed.
In order to overcome these problems, a method of using a toughened glass that has a DOL of about 20 μm with which wheel scribing can be conducted, while having a surface stress of 600 MPa or greater was proposed. However, such a toughened glass also has a problem in that the direction of scribing cannot be controlled since crack-out occurs during wheel scribing when the thickness of the glass is 0.7 t or less, even though the glass can be wheel-scribed at a thickness of 1.0 t or greater.
In addition, in order to overcome this problem, a technology for cutting a toughened glass using a laser can be employed. However, this laser-based cutting technology has drawbacks in that process conditions are very complicated and equipment is very expensive. Therefore, this technology is not appropriate to a manufacturing process that requires a low cost and a high yield.
The information disclosed in the Background of the Invention section is provided only for better understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.